The article describes the first occurrence of hepatic coccidiosis in catfish of the species Brachyplatystoma vaillantii, captured in the coastal region of the Vigia city , state of Pará, Brazil, caused by species of the genus Calyptospora, family Calyptosporidae. Thirty specimens of piramutabas were examined where 60% were infected with liver location, featuring numerous mature and immature oocysts, grouped or isolated, with four sporocysts in pyriform shape. They were described on their morphology and dimensions of the oocysts and sporocysts, obtained from light microscopy and differential interference contrast.

Coccidia comprise a large group of obligate intracellular parasites frequently found in all classes of vertebrate hosts as well as in some invertebrates. Some pathogenic and parasitic forms affect mollusks and fish (MATOS et al., 2004). Indeed, coccidia are common in marine and freshwater fish including the genus Calyptospora (DAVIES; BALL, 1993; MOLNÁR, 2006). The family Calyptosporidae was first described in fishes by Overstreet et al. (1984) and comprises only five species: Calyptospora funduli (OVERSTREET et al., 1984); C. empristica (FOURNIE et al., 1985); C. serrasalmi (CHEUNG et al., 1986); C. tucunarensis (BÉKÉSI; MOLNÁR, 1991), and C. spinosa (AZEVEDO et al., 1993).

Three species of the genus have been described parasitizing the liver of Brazilian fish: C. serrasalmi in Serrasalmus niger (CHEUNG et al., 1986), C. tucunarensis in Cichla ocellaris (BÉKÉSI; MOLNÁR, 1991), and C. spinosa in Crenicicha lepidota (AZEVEDO et al., 1993). Moreover, Bonar et al. (2006) reported the occurrence of Calyptospora sp. and Dawestrema cycloancistrium (Ancyrocephalinae) in seven juvenile specimens of fish species Arapaimagigas (aka pirarucu) which were exported from Manaus to the USA and became ill died four to six weeks after arrival showed lesions mainly in the liver, gills, brain, and gastrointestinal tract. Further, among the most common parasites found in the Amazon fish, Azevedo et al. (1993) found C. spinosa in fish of the species Hoplosternumlittorale (aka tamoatá) and in Crenicichla lepidota (aka jacundá), all naturally occurring in the Amazon River basin.

There is a lack of studies on ictioparasitoses in fish of high economic value such as the one contemplated by this study (Piramutaba Brachyplatystomavaillantii,). Such knowledge is important to correlate disease outbreaks with biotic and abiotic factors and for implementation of necessary mitigation measures to avoid or minimize the impact on fish stocks. Thus, the objective of this study was to describe the morphology of Calyptospora oocysts found in the liver of B. vaillantii, by conventional light microscopy and differential interference contrast and thereby to make an initial assessment of the coccidiosis affecting this fish from the Amazon River basin.

Material and Methods

Thirty specimens of B. vaillantii weighing 380-450 g and measuring between 28.5 and 45.5 cm were captured in the estuary at the Municipality of Nazareth Vigia in the State of Pará, Brazil (00º 51' S and 48º 08' W) by fishermen and donated to this study. The specimens were necropsied following the methods described by Azevedo et al. (1993). To highlight the oocysts, sporocysts, and sporopodium contours we employed differential interference contrast (Nomarski) optics.

Results and Discussion

In fresh preparations of the 18 B. vaillantii specimens found positive for liver coccidiosis and, a large amount of grouped and isolated spherical oocysts were observed (Figure 1a). In many cases, the host hepatic parenchyma was replaced by numerous groups of oocysts, distributed irregularly. Azevedo et al. (1993) found infections in which the liver of the host C. lepidota also held numerous groups of oocysts of Calyptospora sp. arranged irregularly in the liver parenchyma.

Morphological analysis revealed several groups of spherical oocysts, each containing four pirifom sporocysts (Figure 1c), within which sporozoites and sporodiums with lateral projections were found (Figure 1b). Similar findings were reported previously by Azevedo et al. (1993) in C. lepidota, parasitized by C. spinosa. These findings are expected for the genus Calyptospora, which was originally shown to infect fish species by Overstreet et al. (1984).

Measurements showed that the mean diameter of oocyts was 20.8 µm, and the mean length and width of sporocysts were 8.9 and 4.15 µm, respectively. The biometric data obtained from sporulated oocysts were similar to those described by Fournie et al. (1985) regarding C. empristica, Duszynski et al. (1979) for C. funduli, Cheung et al. (1986) for C. serralsalmi, Békési and Molnár (1991) for C. tucunarensis, Azevedo et al. (1993) for C. spinosa, Bonar et al. (2006) for Calyptospora sp. and Albuquerque and Brasil-Sato (2010) for Calyptospora sp.

Table 1 shows the comparative biometric data regarding sporulated oocyst size and shape, and sporocyst length and width, of the Calyptospora species described in the literature. A new morphological and structural description of C. serrasalmi revealed mean oocyst diameter of 25.4 µm (CASAL et al., 2007). Although the mean oocyst size found in the present study is smaller than that reported by Casal et al. (2007), it is similar to that described for C. spinosa by Azevedo et al. (1993). Analyses of shape and size of spocysts revealed they were similar to those reported for C. serrasalmi by Cheung et al. (1986) and Calyptospora sp. by Bonar et al. (2006), both studying Brazilian fishs.

The morphological and biometrical characteristics of the oocysts and sporocysts observed by light and Normarski microscopy, suggest that they belong to species of the genus Calyptospora; since coccidia oocysts of this taxonomic category are spherical and of similar size; and each contain four sporocysts. This finding corroborates the evidence reported by Azevedo et al. (1993), who noted the morphological similarity between sporocysts of C. fundulea, C. empristica, C. serrasalmi, and C. tucunarensis, also observed in this study.

Conclusion

This study extend the occurrence of Calyptospora sp. for a new Neotropical host, the piramutaba B. vaillantii.

Acknowledgements

This study was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior pela bolsa de estudos (CAPES). We thank the Instituto Acquamazon for providing access to the fish, the Laboratório de Pesquisas Aquáticas Carlos Azevedo of the Universidade Federal Rural da Amazônia for helping with the histopathological studies, and the Laboratório de Microscopia Eletrônica do Instituto Evandro Chagas for help with Normaski optics and the Andrea Kaufmann-Zeh PhD. for revising the English translation.